keer n-ereeitt



Patented Sept, 12, 1922,

Ivan. RnnN-E'Rrnnr, o r

nJunsn'oLM; swan nu.

METHOD OF OPERATING ELECTRIC FURNACES.

' 'NoDrawing Application filed Au ust 12, 1921. Serial No. 491,837.

seamen nurse was rnovrsrous or run sum or MARCH 3, 1921, 41 simian, 1313.

' To aZl w-lw'm it may comm: Be it. known that 3:, Ivan Rnnnnnrnn'r, a-

citizen of the Kingdom' of 'Sweden, and

resident of.Djursholm, in the county of Stockholms Lam. and Kingdom of Sweden,

have invented a new and useful Method ofbe'us'ed preferably for melting and refining meta-ls.

According to my method plurality of arcgenerating, adjust-able electrodes are pro-I vided in a furnacerooni, being so arranged that arcs may be caused to burn either be tween thetips of the electrodes or between v the electrodes and a charge underneath the electrodes,

My intention consists, furthermore and pri.ncipa lly,in providing means for supplying either twophase or threephase current to said electrodes. This may be obtained. by providing two separate transformers, one for delivering twophase current and another for deliveringthreephase current to the furnace, and als'o suitable switching device in combi nation with the two. transformers. It is possible alsp to employ for the same purpose one single transformer, consisting of two separate singlephase units, which may be connected together either according to the wellknown Scott system or according to what is'called i open delta connection. The former connection is used for: delivering twophase currenty the latter for delivering threephase current.

Several adyantages, are secured by operating an arciumace with both twophase and threephase current. In the case of melting a cdld charge the use of twophase current simplifies theregulation of the input 'of energy, as only two electrodes {will have to be. regulated in case the I electrodes 'are arranged as disclosed for instance in U. S.

Patent 1 ,l03,37 9. 'The'threephase current is to beiifsed for generatingfarcs, preferably but not alway's, in contact with the charge the number of arcs being equal to the numto the patent cited above, three arcs will be available for refining a liquid charge if using threephase current, whereas only two arcs would be available, if using twophase current all thetime. It is tobe noted that twophase arcs in contact with the charge may he used in such a case only, if the electrode connected to the common terminal of the secondary transformerwinding, is shortclrcuited with the charge. This, however, will sometimes cause difficulties by the chargeabsorbing carbon from the electrode,

which 1511'1 immediate contact.

The use of three-phase current norrefinin a charge, which has been previously melte by 1 means of twophase current reburning arcs, will cause a vigorous stirring of the surface layers of the charge greatlyfacil-itating severalof the reactions required for refinding a charge of'steel. It is possible to move the tips of the electrodes with relation to; eachxother, in this way altering not only the intensity of heating at the central part of the charge but also the resistance to the flow 0% the'electric current between any two of the electrodes.

' It obviously isalconsiderabl be able to. distribute the heat bymeans oi at least three separate arcs instead of heating e advantage to the furnace all the time with a twophase arc,,concentratedat the central partof thecharge and burningireely abovethe'surface- I do not mean} however, that the furnace should be operated wi threep'hase arcs in contact with the charge: all the use after acold charge hasbeen meIted', as it: nay be advisable for obtaining a minimum of slag inclusions to let the gsteelbath" remain ,in quietness for a considerable killing time, being heated by means of freeburniiig arts, which have no tendency. to cause undesirable Whirlin the steei out changing back from. threephasecurrent supply to twophase current supply. This may even beadvisable as a lower voltage may very conveniently be obtained from a' motions in the bath. 'For. killing I freeburn'ingarcs may be used with transformer, built to supply eithertrophase Y or threephase current. The use of a lower voltage is tobe preferred during the finishing of the charge as this will facilitate the arc furnace consisting in first supplying prevention of too high a temperature being twophase current and then supplying threeused. phase current employing arcs in contact I do not want to limit myself to any with the charge.

5 specific methodof obtaining alternatingly 3. The method of operating an electric twophase or threphase current as this may furnace consisting in supplyin first two- -be done in any preferred way. I also donot phase current heatin a charge y means of limit myself to the use of any certain numfreeburning arcs an then supplying threeber of electrodes as evidently a multiple of phase current heatin the charge by means 10 three electrodes arranged in sets of three of arcs in COHlI-HCt WIlIh the surface of the electrodes each may be provided especially charge and changing the relative distance in large furnaces. between the arcs.

aying now fully described my invention, Signed at Stockholm in the county of I claim and desire to secure by Letters Stockholnis Lau and State of Sweden this '15 Patent of the United States: 3b.- dayof July A. D. 1921.

1. The method ofoperating an electric arc furnace consisting in first supplying to the electrodes twophase current and then \Vitnesses: supplying threephase current. S. IVERSON, 20 2. The method of opaurating an electric AMPTON BONNER.

VAR BEN N ERFELT. 

